When I voted here in Australia you didn't need any id. They just ask your name, street address, and whether you've already voted anywhere else (I'd like to see someone say yes!). But voter fraud has never been much of an issue here. I think with compulsory voting it would probably be really hard to do, and wouldn't make a sufficient impact to be worthwhile.
On that note, what are people's opinions on compulsory voting. Personally I think it should be a democratic requirement - that way the government truly does represent the majority of the population. And if you want to lodge a protest vote (ie write your ideas about how the political system could be improved or whatever) ok, so your vote will be invalid, but the inspectors have to check all the votes, so you can be guaranteed someone will take notice of what you've written.
Lastly, here in Oz we heard stories of people lining up for hours and hours to vote in America. Why does this happen in a country where only a certain percentage of the population votes, whereas here, where everyone votes, I was able to walk straight into a polling booth, get my name checked off, vote, and walk out without having to wait at all.